The present invention relates to the electrolytic chlorination of alkyl aromatic compounds to produce para-chloroalkyl aromatic compounds.
Para-chloroalkyl aromatic compounds generally are useful intermediates in the production of organic chemicals, and are especially important intermediates in the production of certain biologically active compounds.
Alkyl aromatic compounds have been monochlorinated electrolytically in the past. Gourcy et al. in Electrochimica Acta, Vol. 24, 1039-1046 (1979), report the anodic chlorination of benzene and its methyl-substituted derivatives in acetonitrile/LiClO.sub.4 electrolyte using a platinum anode. The chlorinating salt was LiCl or tetraethyl ammonium chloride. At page 1040, it is taught that: "In the case of toluene, the orthochloro derivative is formed in preference to the parachloro derivative." This conclusion was reached from the observation of experimental runs in which the potential was 1.5 volts or higher.
Higher para-chloro/ortho-chloro (hereinafter p/o) ratios are achieved using the process of U.S. Pat. No. 4,269,674. Said process is disadvantageous in that it operates at very low conversions, and requires an anode of a carbonaceous material having cyclodextrin or a derivative thereof bonded onto the surface of the anode. These exotic cyclodextrin-containing electrodes are disadvantageous in that their preparation involves several steps and the electrodes have a limited useful life. Consequently, it would be expensive to use the cyclodextrin-containing electrodes in a commercial process.
In view of the deficiencies of the electrolytic chlorination methods of the prior art, it would be desirable to have a process to produce monochlorinated alkyl aromatic compounds at good conversions and with high p/o ratios using standard, readily available electrodes.